1. Field of the Invention
The present invention relates to an image forming apparatus for forming a toner image on a recording material.
2. Description of the Related Art
A recording material discharged immediately after a toner image formed on the recording material has been heated and fixed is at a high temperature. In normal circumstances, immediately after the heating and fixing process, the recording material is discharged to a discharge tray by, e.g., a discharge roller. Accordingly, high-temperature recording materials are stacked on the discharge tray, and the toner image that has been heated and fixed onto the recording material may be melted again by the high-temperature recording materials that have been discharged, and the toner image may stick to the back surface of the recording material.
In order to solve such a problem, external air that has been drawn by, e.g., a fan, is blown onto the recording materials discharged onto the discharge tray to cool the recording materials, so that the toner image that has been heated and fixed on the recording material is prevented from being melting again.
For example, Japanese Patent Laid-Open No. 2005-77565 indicates that a cooling fan cools a portion around a discharge roller provided downstream of a fixing device, and in accordance with whether a discharge device is attached or not, the flow of air from the cooling fan is changed.
When a high-temperature recording material is stacked on a discharge tray, a toner image heated and fixed on the recording material is melted again by high-temperature, previously-discharged recording materials. Accordingly, the toner image attaches to the back surface of the recording material. In order to prevent this, the recording material is cooled by blowing external air, which is retrieved by, e.g., a fan, onto the recording material discharged onto the discharge tray, and the toner image heated and fixed on the recording material is prevented from being melted again.
However, when the recording material is cooled, the discharge roller and the like are also cooled, and therefore, unevenness of cooling occurs in the toner image because of the difference in the temperature between the recording material discharged immediately after the heating and fixing process and the discharge roller and the discharge driven roller, and failure may occur in the image, e.g., the occurrence of contact marks of the discharge roller and the discharge driven roller.
The present invention solves the above problem, and it is desirable to cool the recording material on which the toner image has been heated and fixed and which has been discharged, and the toner image, which has been heated and fixed on the recording material, is prevented from being melted again. Further, the present invention provides an image forming apparatus that prevents the conveying portion from being cooled, thus preventing unevenness of cooling of the toner image, and preventing the making of any contact mark of the conveying portion.